Atlanta - If you or your neighbor installed a wood fence in the last decade, consumer Channel 2’s consumer investigator Jim Strickland says that you should look for signs of rot.

That's because 10 years ago a federal law changed the chemicals used to treat exterior lumber.

It's healthier, but contractors warn that the new treatment isn't working.

"The old stuff was the good stuff," said fence contractor Dave Tibbetts.

He showed Strickland a fence post he installed eight years ago. Every inch in contact with the ground was rotten. The next fence post from a fence in Cobb County was sheared off from decay.

"So far we know 12 posts are rotten, but I counted like 40 posts. It could be a lot more than that," said homeowner Todd Ryan.

In January 2004, the Environmental Protection Agency banned wood treatments made with arsenic. Copper dissolved in the poison had been a common wood preservative for decades, but concern grew that it was leaching into the soil near children's wooden play sets.

Ten years after a series of substitute chemicals hit in the market, the American Wood Protection Association confirmed there have been complaints that the substitute chemicals are failing.

"I think this is the tip of the iceberg," said Tibbetts as he worked to replace a rotting post.

The standard industry warranty only replaces the post. It doesn't pay for labor. Tibbetts is doing replacement jobs at cost.

"This is just crazy. It is not a little rot, this post is disintegrating after eight years in the ground," said Ryan.